U.S. Pat. No. 4,520,022 disclosed 3-[(Z)-1-propen-1-yl]-7-acylamido cephalosporins. These compounds are antibacterial agents. Among them Cefprozil, chemically (6R, 7R)-7-[2-amino-2-(4-hydroxyphenyl)acetamido]-3-[(Z)-propenyl]-3-cephem-4-carboxylic acid is an orally effective cephalosporin antibiotic having a broad spectrum of antibacterial activity against both gram-positive and gram-negative organisms. Cefprozil is represented by the following structure:

Processes for the preparations of cefprozil, it's hydrates and related compounds were described in U.S. Pat. No. 4,727,070, WO 98/04732, U.S. Pat. No. 4,694,079 and GB 2173798. U.S. Pat. No. 4,694,079 disclosed a process for the preparation of DMF solvate of cefprozil. U.S. Pat. No. 5,608,055 disclosed a process for the preparation of 7-α-acylamino-cephalosporin by acylating 7-amino-3-cephem-4-carboxylic acid or a derivative thereof in a halogen-free solvent. According to U.S. Pat. No. 4,148,817 the silylation of [R-(Z)]-[4-hydroxy-α-[(3-methoxy-1-methyl-3-oxo-1-propenyl)amino]]benzeneacetic acid, mono potassium salt (amoxydane salt) can be done properly with hexamethyldisilazane and trimethylsilyl iodide and the silylated salt is converted into a mixed anhydride; and the patent also disclosed that the use of N,O-bis(trimethylsilyl)acetamide in the silylation results in the development of color which cannot be removed. Moreover the process as per U.S. Pat. No. 4,148,817 requires isolation of silylated amoxydane salt intermediate before converting to silylated anhydride.
All the aforesaid patents are incorporated herein by reference.